The human eyes may take a period of time to adapt to brightness variation from one lighter image to one darker image displayed on a display device; similarly, the human eyes may also take a period of time to adapt to brightness variation from one darker image to one lighter image displayed on the display device. Generally, a process that the human eyes adapt to variations between light and dark is called as brightness adaption. One process that the human eyes adapt to variation from light to dark is called as dark adaption, and one process that the human eyes adapt to variation from dark to light is called as light adaption. The process of light adaption lasts for only a few seconds (generally less than one minute); however, the process of dark adaption may last for a relative long period of time. According to different initial brightness, the dark adaption of the human eyes may generally last for more than 5 minutes.
When a user watches a display device, screen brightness of the display device may vary in real time along with variations of contents displayed on the display device. When the user watches the display device indoors, the indoor brightness remains unchanged and cannot be adjusted, therefore, when there is a large contrast between the screen brightness of the display device and the indoor brightness, the pupils need to keep adjusting to adapt to the screen brightness of the display device and the indoor brightness simultaneously, so as to adapt to variations from light to dark and from dark to light, which will certainly lead to that the adjustment of the pupils lags behind the brightness variations. At this point, the screen brightness variations of the display device will make a great irritation to the human eyes, thereby harming the human eyes.